Category Archives: Apple II

About Early Apple II computers

SCELBI TTY and Apple II Serial Card Update

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I now have SCELBI TTY cards in stock and will ship one to you for $30, shipping included. If you are interested send an email to: mike@willegal.net. Be aware that at this point they are not tested, so until I get one tested, I don’t guarantee that they will work without modification.

Regarding TTY card testing, I have been delayed because I didn’t have a current loop interface to test it against. Well that has been rectified, as I have the Apple II Serial Card that I mentioned in another post working (at least in RS232 mode). In order to get that card working in a way that would work for interfacing to the SCELBI TTY card, I had to reconstruct and burn a P9 PROM that matched the first version PROM. Wendell Sander was nice enough to send me a PROM that was a copy of his serial card P9 PROM. However, his P9 PROM was overwritten in a couple of spots with a all ones pattern. I took his PROM and compared the parts that were intact with the listing at the back of the manual and determined that I could resurrect his PROM by filling in the missing code with the code from the listing in the manual. After messing up my first attempt, I burned what I thought was a good P9 PROM. I put it in the Serial card and tested in RS232 mode against a Super Serial card in another Apple II. That simple test was successful and I now have a working Apple II Serial card without the undesirable flow control behaviors of the second version PROM.

I should be able to use this card in current loop mode for testing the SCELBI TTY card. In fact, I have visions of putting it in an APPPLE IIe (for the needed 72 column support) and emulating TTY operation as closely as I can with the Apple II. I should be able to emulate not only print and typing functions, but emulate paper tape as well. Potentially, I could even add a real paper tape reader and possibly punch by constucting an interface on a SUPERPROTO board.

As far as my prototype TTY card itself, it is mostly built up, just missing a couple of resistors which should arrive today or tomorrow. Once it’s together and tested I’ll put up a Bill of Materials, some simple build instructions and photos.

Apple II Serial Card Initialization Details

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While looking for a way to test the SCELBI current loop interface, I discovered that an early Apple II peripheral card, the Serial Interface Card, supported current loop. This card was designed to interface to printers and supported half duplex baud rates up to 19200 baud. Since I only need 2400 baud for SCELBI and the SCELBI only supports half duplex, I thought that I could use it for testing the SCELBI TTY interface card.

I found that I had a serial interface card in my stash and tried it out, using the RS232 mode to see if it would work. However I found that it would only output 1 byte and then hang. I had a friend who scanned the manual for me and sent a PDF to me. Looking over the manual at first, I couldn’t determine what was wrong. However dumping the firmware revealed that the firmware was different than that listed in the manual. After some web searches, I determined that there was a second version of the firmware that supported RTS/ACK software handshaking and that this second version did not work with some printers.

Since I couldn’t find a copy of the second version’s manual, this started me off on an reverse engineering investigation. This was a more difficult process than I first anticipated. Along the way I learned about some clever 6502 programming tricks, including a way to implement a primative 6502 skip instruction. I also have come up with a partly annotated listing that may be of interest to Apple II peripheral interface designers. This doc details some of the tricks involved in initializing Apple II interface cards. As the input and output functions are not of much interest, they are not well documented.
Apple Serial Interface Firmware

By the way, with the second version of firmware, there is no way to disable the RTS/ACK software handshake, so I’m going to have to find or make a copy of the first version firmware to test my SCELBI current loop interface.

Say Hi At VCFse in the Atlanta Area

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This year, for the third year in a row, I’ll be leaving the family in the care of our dog, Toby, and be spending a weekend with fellow retro-computer hobbyists. Since this years VCFeast, had to be cancelled, I’ll be treking down to VCF southeast in Atlanta for the weekend of April 20 and 21st. These weekends are always fun, so I highly encourage everyone that might be interested in these things to make the effort to join us.

Here is the link with informaiton for that event.
http://vintage.org/2013/southeast/

Stop by my exhibit. I’ll be operating a Mimeo 1 and a reproduction SCELBI 8H (one of a very few working SCELBIs in the world). I’ll even give you a chance to “drive”. Tell me you read my blog and get a free SCELBI/8008 reference card.

See you there…

PS/2 Adapter Repurposing

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The daunting task of toggling in a program of any significant length into a SCELBI has made me consider ways of automating the process, at least for demonstration purposes. What I’m looking at, is altering the program on one of my PS/2 to ASCII keyboard adapters and connecting it to the SCELBI’s front panel connections. Here are the reasons why I think this will work out really well.

  • The front panel is controlled through TTL I/O lines pulled up to +5 volts with 1k resistors. This is something that the AVR should be able interface directly to.
  • There are more than enough I/Os available on the PS/2 card, especially if I repurpose the three configuration jumpers. There are 8 bits for data and three pushbuttons for control. In addition I should be able to tap into a couple of the CPU status lines in order synchronize with the CPU states.
  • I already have both keyboard and RS232 drivers written for this board.
  • The keyboard can be used for control and the RS232 port to get data from a host computer.
  • An alternate approach is to use RS232 for both data and control.
  • I have plenty of these boards available. I’ve used less then half of the lifetime supply that I had made when the Mimeo first came out.

    • The interesting thing about this little board, is that I can also use it for other interface applications on the SCELBI, at least until I have time to reproduce authentic 70s era interfaces that were available. Examples include:

  • RS232 interface
  • With a bit of extra hardware – cassette tape interface

    • Beginning of Year Retro Update

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    Mimeo’s

    Last weekend, I sold the last of the Mimeo PCBs (Glossy and Matte) that I had in stock. I will make some more matte after I’ve sold some of the first batch of the SCELBIs. I’m down to 4 ACI cards, so I’ll have to do a batch in matte to go with the next batch of Mimeos.

    The new movie, “jOBS” will premiere at the Sundance Film festival this month. I’m hoping that the Mimeo PCBs that I sold to the prop house supporting the film, get some screen time and the film is good enough to get some decent reviews.

    I still have plans to do a full built up system, but that project will have to wait until I have the SCELBI going. I am sorry that this has been teaser for some folks who have been waiting for it. However, I’m hoping that when I finally get to it, that folks will be impressed with the results, and say that the wait was worth it.

    The new run of Datanetics PCBs have been trickling out, maybe a little faster than I expected, given the difficulty of finding components. They have mostly been combined with Mimeo PCB sales. I really wonder how many will get built up. This datanetics PCB batch has been done more of a service to the retro community, as it will be a while before this project breaks even financially.

    SCELBI

    Quotes from Advanced Circuits on SCELBI boards are about half of what I expected, which is awesome. Nashua Circuits came in as expected, so I guess Advanced will get this business, unless Nashua can do much better (I’ll give them a chance to improve their quotes). Since there is no solder mask, it really shouldn’t make much of a difference who makes them.

    Design checks on the base 5 board set is done, and I’m about ready to declare victory on the layout tweaking/matching. The 8H backplane is just about ready, so I’ll probably get a batch of those made to go with the base 5 board 8H set, making it a 6 board set. The backplane has been challenging, as there is no schematic, only a wire list intended for wiring your own chassis. Good images of the top of backplane are non-existant. My orders for the PCBs may go in, as early as this week.

    I do have one thing to check on the CPU board. There were at least two versions of the CPU board made, I am replicating a later version. There is a report of an issue with the step function reported SCELBI digest, issue II. Though describing a problem in a later version of the CPU board, this report shows a slightly different design than the one in the version of the schematics/layout that I am replicating. I just need to make sure the schematics that I’ve followed are accurate.

    At this writing, estimates for the set of 6 PCBs, with an 8008D thrown in, but no other components, is in the range of 300 dollars. Final price might vary a bit, but I doubt that I could make it go any lower, without making this a one off effort, not to be repeated.

    A friend of mine, is looking into doing a reproduction bezel for the front panel of the chassis. He tells me that there are some challenges, as the original was anodized, and most panel manufacturers, these days, do powder coating.

    Today, I am going to see if I can generate a BOM (bill of materials) in an excell spreadsheet. Except for the 8008 and memory, I think most of the rest of the electronics components are readily available. I plan on sending the BOM to Unicorn, who have indicated, a while back, that they would do parts kits for this project, like they have for the Mimeo/Apple 1. The relay sockets used for I/O ports in the chassis, are available, but expensive – I’m going to see if I can find a way to get bulk price on those from someone.

    The 8B will follow on the heals of the 8H, It uses the same front panel, CPU, DBB, and input boards as the 8H, but requires 4 new boards…

  • new backplane with an extra slot for the memory addressing board. I haven’t investigated in detail, but I hope I can leverage most of the 8H backplane design, making this pretty straightforward
  • new 4K memory module. I already have done the base chip placement for this one
  • PROM board. Cameron Cooper has a draft design, that he says he will let me leverage
  • memory address expansion card – haven’t started

    • All in all, you can see that based on the head start that I have on the 8B boards, this shouldn’t take nearly as long as the 8H has taken, to complete.

    After these are done, there is more SCELBI hardware to be done, a TTY interface, a scope interface and a cassette interface. Power supplies are another potential future project. For now you will need to find a 5 volt and -9 volt supplies. Amperage ratings depend upon the amount of memory and peripherals. According to SCELBI documentation, system with a keyboard, oscilloscope interface, and cassette interface requires the following.

  • 4K memory requires 5 volts at 6 AMPs and -9 volts at 3 AMPs
  • 1K memory requires 5 volts at 3 AMPs and -9 volts at 1 AMP

    • I’m also likely to do an automated front panel controller with a micro-controller, to make loading the memory on the 8H easier. I might be able to reuse my existing PS/2 adapter with a new program in order to accomplish this.

    Brain Board

    Brain Board stock is dwindling, but sales have been very slow, as of late. When the stock runs out, I’ll definitely hold off on making a new run, until demand builds up again.

    SUPERPROTO

    So far, interest has been a bit lighter than expected. However I’ve got wind of a couple of super cool SUPERPROTO based projects, that may just jumpstart sales when the projects are publicly announced. Feedback from folks using the card has been positive, with no unexpected problems or issues reported. I also know of one, well known, Apple II hardware designer that is leveraging parts of the design, which I have published in detail on the SUPERPROTO Wiki, for his next efforts. Even though, I get no financial reward from this leveraging, it is gratifying to know that my efforts are of use to others.

    Apple II rev 0

    A rerun of these PCBs is also in the cards, though I want to make a few tweaks, so it will also come after the SCELBI and probably the fully built Mimeo.

    That is all the retro stuff that I can think of, for now – Happy New Year

    Looking for Uncracked John Madden Football for Apple II disk images

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    I recently got a hold of a copy of the game, but the floppy isn’t good, so I need to either reformat and rewrite the old disk or create a new disk. I have the azimov cracked version, but would really like to get a copy of the original version. Note that there is no copy protection on the disk itself – it uses a code wheel to enable play of the game (which is what was hacked out).

    Either a hard copy of the disk or a DSK image would be be helpful.

    If you have this disk image or know where to get it, send email to:mike

    New Datanetics PCBs Due in 2-3 Weeks!

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    Despite very limited demand for these keyboard reproductions, I decided to pull the trigger on another batch. I think I am having more than enough made for everyone that has expressed interest, but in any case, let me know, if you are seriously interested in getting one or more.

    This time, I will be only selling blank PCBs, no brackets or anything else, so these are for the advanced hobbyist, only. I may do a brief instruction sheet, if I have time, but most of the info needed to build one up, is already on this blog (check the Datanetics category) or my website. I have to think some more about price, but I expect they will be around $80, including shipping. Even to me, this seems high for a blank PCB. However, keep in mind that these are fairly big boards by modern standards, and I only make a few in a batch.

    Like all my PCBs, they are made to a very high quality standard, right here in the USA.

    Updates to Apple 1 Registry

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    While sitting around at the court house on jury duty, I took the opportunity to update the Apple 1 Registry. Besides some general cleanup, I added interesting images of a unit in a rack mount enclosure. Associated with this unit is a letter from Apple indicating that there was no trade ins available, as of April, 1979.

    http://www.willegal.net/appleii/apple1-originals.htm

    PS – I was tempted to dedicate a post to rant about America’s wasteful judicial system, but they are just trying to enforce the hundreds of thousands of laws our law makers have made up over the years – a hopeless task.